研究人员探寻新的、稳定的元素
文章来源:未知 文章作者:meng 发布时间:2010-02-12 02:04 字体: [ ]  进入论坛
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Besides the 92 elements that occur naturally, scientists were able to create 20 additional chemical elements, six of which were discovered at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt. These new elements were produced artificially(人为地) with particle accelerators(粒子加速器) and are all very short-lived: they decay in a matter of a split second. However, scientists predict the existence of even heavier elements with an extreme longevity1(寿命,长寿) , leaving them to only decay after years. These elements form an island of stability. Scientists at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt have developed and applied2 a measuring apparatus3(测量仪器) that might allow them to discover such long-lived elements, reports the renowned4(著名的,有声望的) scientific journal Nature. An international team of scientists headed by Michael Block was able to trap atoms of the element 102, nobelium(锘) , in an ion trap(离子捕集器) . This is the first time in history that a so-called super heavy element had been trapped. Trapping the element allowed the research team to measure the atomic mass of Nobelium with unprecedented5 accuracy. The atomic mass is one of the most essential characteristics of an atom. It is used to calculate the atom's binding6 energy, which is what keeps the atom together. The atom's binding energy determines the stability of an atom. With the help of the new measuring apparatus, scientists will be able to identify long-lived elements on the so called islands of stability that can no longer be assigned by their radioactive decay(放射性衰变) . The island of stability is predicted to be located in the vicinity of(在附近,在上下) the elements 114 to 120.

„Precisely measuring the mass of nobelium with our Shiptrap device was a successful first step. Now, our goal is to improve the measuring apparatus so that we can extend our method to heavier and heavier elements and, one day, may reach the island of stability", says Michael Block, head of the research team at the GSI Helmholtz Centre.

For their measurements, Michael Block and his team built a highly complex apparatus, the ion trap "Shiptrap", and combined it with "Ship", the velocity7(速率,周转率) filter which was already used in the discovery of six short-lived elements at GSI. To produce nobelium, the research team used the GSI accelerator to fire calcium8 ions onto a lead foil. With the help of Ship, they then separated the freshly produced nobelium from the projectile9(抛射的,抛掷的) atoms. Inside the Shiptrap apparatus, the nobelium was first decelerated in a gas-filled cell, then the slow ions were trapped in a so-called Penning trap.

Held inside the trap by electric and magnetic fields, the nobelium ion spun10 on a minuscule11(极小的) spiral(螺旋形的) course at a specific frequency. This frequency was used to calculate the atomic mass. With an uncertainty12 of merely 0,000005 per cent, this new technique allows determining the atomic mass and binding energy with unprecedented precision and, for the first time, directly without the help of theoretical assumptions.



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1 longevity C06xQ     
n.长命;长寿
参考例句:
  • Good habits promote longevity.良好的习惯能增长寿命。
  • Human longevity runs in families.人类的长寿具有家族遗传性。
2 applied Tz2zXA     
adj.应用的;v.应用,适用
参考例句:
  • She plans to take a course in applied linguistics.她打算学习应用语言学课程。
  • This cream is best applied to the face at night.这种乳霜最好晚上擦脸用。
3 apparatus ivTzx     
n.装置,器械;器具,设备
参考例句:
  • The school's audio apparatus includes films and records.学校的视听设备包括放映机和录音机。
  • They had a very refined apparatus.他们有一套非常精良的设备。
4 renowned okSzVe     
adj.著名的,有名望的,声誉鹊起的
参考例句:
  • He is one of the world's renowned writers.他是世界上知名的作家之一。
  • She is renowned for her advocacy of human rights.她以提倡人权而闻名。
5 unprecedented 7gSyJ     
adj.无前例的,新奇的
参考例句:
  • The air crash caused an unprecedented number of deaths.这次空难的死亡人数是空前的。
  • A flood of this sort is really unprecedented.这样大的洪水真是十年九不遇。
6 binding 2yEzWb     
有约束力的,有效的,应遵守的
参考例句:
  • The contract was not signed and has no binding force. 合同没有签署因而没有约束力。
  • Both sides have agreed that the arbitration will be binding. 双方都赞同仲裁具有约束力。
7 velocity rLYzx     
n.速度,速率
参考例句:
  • Einstein's theory links energy with mass and velocity of light.爱因斯坦的理论把能量同质量和光速联系起来。
  • The velocity of light is about 300000 kilometres per second.光速约为每秒300000公里。
8 calcium sNdzY     
n.钙(化学符号Ca)
参考例句:
  • We need calcium to make bones.我们需要钙来壮骨。
  • Calcium is found most abundantly in milk.奶含钙最丰富。
9 projectile XRlxv     
n.投射物,发射体;adj.向前开进的;推进的;抛掷的
参考例句:
  • The vertical and horizontal motions of a projectile can be treated independently.抛射体的竖直方向和水平方向的运动能够分开来处理。
  • Have you altered the plans of the projectile as the telegram suggests?你已经按照电报的要求修改炮弹图样了吗?
10 spun kvjwT     
v.纺,杜撰,急转身
参考例句:
  • His grandmother spun him a yarn at the fire.他奶奶在火炉边给他讲故事。
  • Her skilful fingers spun the wool out to a fine thread.她那灵巧的手指把羊毛纺成了细毛线。
11 minuscule V76zS     
adj.非常小的;极不重要的
参考例句:
  • The human race only a minuscule portion of the earth's history.人类只有占有极小部分地球历史。
  • As things stand,Hong Kong's renminbi banking system is minuscule.就目前的情况而言,香港的人民币银行体系可谓微不足道。
12 uncertainty NlFwK     
n.易变,靠不住,不确知,不确定的事物
参考例句:
  • Her comments will add to the uncertainty of the situation.她的批评将会使局势更加不稳定。
  • After six weeks of uncertainty,the strain was beginning to take its toll.6个星期的忐忑不安后,压力开始产生影响了。
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